Added 'email sending test' functionality.

Go to Admin -> Mail notifications and click on 'Send a test email'.
If an error occurs while sending the mail, the error message is displayed to the user.

git-svn-id: http://redmine.rubyforge.org/svn/trunk@632 e93f8b46-1217-0410-a6f0-8f06a7374b81

app/models/mailer.rb

@@ -113,4 +113,11 @@ class Mailer < ActionMailer::Base
     @subject        = "[#{message.board.project.name} - #{message.board.name}] #{message.subject}"
     @body['message'] = message
   end
+  
+  def test(user)
+    set_language_if_valid(user.language)
+    @recipients     = user.mail
+    @from           = Setting.mail_from
+    @subject        = 'Redmine'
+  end
 end